Problem: $ 5^{-3}$
Explanation: $= \left(\dfrac{1}{5}\right)^{3}$ $= \left(\dfrac{1}{5}\right)\cdot\left(\dfrac{1}{5}\right)\cdot \left(\dfrac{1}{5}\right)$ $= \dfrac{1}{25}\cdot\left(\dfrac{1}{5}\right)$ $= \dfrac{1}{125}$